Okay putting methoxy estra tetratraen into google yielded the following (and many more organic chemistry sythesis papers):
I also found six other methoxy-estra-tetraen-one compounds with the keto group in position 17 and the methoxy group in position 3 (from the Dictionary of Steroids By R. A. Hill, Anthony Cooper).
Dictionary of steroids - Google Books
3-methoxyestra-1,3,5(10),7-tetraen-17α-one
3-methoxyestra-1,3,5(10),8-tetraen-17α-one
3-methoxyestra-1,3,5(10),8(14)-tetraen-17α-one
3-methoxyestra-1,3,5(10),9(11)-tetraen-17-one
3-methoxyestra-1,3,5(10),14-tetraen-17α-one
3-methoxyestra-1,3,5(10),15-tetraen-17α-one
Only the top one is derived from Equilin. The second and third ones are probably derived from an other horse estrogen, Equilenin. The fourth seems to be the product of microorganism degradation of estratrienes or of androstadienes. The last two are probably derived from Estradiol.
Several of these are also listed in The Dictionary of Natural Products By J. Buckingham.
Dictionary of natural products - Google Books
3-methoxyestra-1,3,5(10),7-tetraen-17α-one
3-methoxyestra-1,3,5(10),9(11)-tetraen-17-one
I found other 3-methoxyestra-1,3,5(10)__-17-one compounds, but they all seem to be totally synthetic.
And of course, I found this:
3-Methoxy-Estra-1,3,5(10),16-tetraene
I’ll keep looking.
Diane